another victim, 29-year-old krystle campbell, is also being remembered. she was at the marathon cheering on her friend's boyfriend. >> we can't believe this has happened. she was such a hard worker at everything she did. this doesn't make any sense. >> reporter: the third person killed has been identified as a boston university graduate student from china. this morning authorities are piecing together more clues. abc news has obtained these photos of a shredded backpack and pressure cooker that was modified and used as one of the bombs. >> it appears that this device may have been dropped in a backpack either inside the trash cans or right outside the trash cans. >> reporter: an fbi advisory